Thermal switch



H. W. WEBB.-

THERMAL SWITCH.

'APPLICATION FILED MAR. Ill, I9I8.

Patented Feb. 10,1920.

//f/ ATTORNEY UNITED sTATEs PATENT oEErcE.

' HAETWELL w; WEBB, oF cEEssKILI'., NEW JERSEY.

THERMAL SWITCH.

To all whom it may concern.'

Be it known that I, HARTWELL W. WEBB, a citizen of the United States, and a resident of Cresskill, in the county of Bergen and State of New Jersey, have invented certain signed for periodically opening vand closing of electric circuits, `for instance those of the electric lamps of a sign or otherI electrically operated advertising devices; y

In the devices of4 this type heretofore in use, electric heaters have been employed which necessitate` for operation a considerable ainount of heat. Inasmuch as the heat activity, or the heat-per-second, produced by an electric current is proportional to the electric power or the watts, it is obvious that these switches could be inserted only in lsuch circuits which are 'of high electric power.

The main object of the present invention s to produce a thermo-dynamic switch which can be made use of in connection with low electric power circuits, such as for instance with pocket Hash lights, or generally in connection vwith a few dry batteries or secondary cells. 4

Another'object of the invention is to produce a switch of the character described, which is simple in construction, inexpensive to manufacture, and which is capable of withstanding rough usage without getting out of order.

A further object of the invention is to so construct the'switch that its frame members constitute at the same time the terminals thereof, thereby being capable' of insertion into the circuit of pocket ash lights without necessitating the provision of `special clamps or terminal screws. K

With these and other objects in view, which will more fully appear as the nature of the invention is better understood, the

4same consists in the combination, arrangement, and construction ofparts hereinafter described, pointed out in the appended claims and illustrated in the accompanying drawings, it being understood that many changes may be made in the size and proportion of they several parts and details of construction within the scope ofthe ap-v Specication o'f Letters Patent.

Application led March 11, 1918. Seria] No. 221,743.

Patented Feb. 10, 1920.

pended claims without departing from the spirit or sacricing any of the advantages of the invention. l l

One of the many possible embodiments of the invention is illustrated in the accompanying drawings, in which Figure 1 is a top plan view of a switch constructed in accordance with the present invention; Fig. 2 is a section taken on line 2-2 of Fig. l; Fig. 3 is a section taken on line 3-3 of Fig. l; Figfll. is` a perspective view of a section of one of the conductors of the switch; Fig. 5 is a perspective View of another section of the conductor cooperating with that shown in Fig. 4 of the drawings; and Fig. 6 is a diagram illustrating the manner of connecting the improved l metal, and being preferably of disk shape,

so as to be insertible into pocket flash lights of thecylindrical type. From this plate rises a lug 11, shown in the present case as being made integral with the base plate, a1- though this feature is not essential.'- The lug is bent substantially at right angles to the base plate and is provided with a screw threaded hole 12. With the threads of this hole mesh those of a screw bolt 13, that extends in radial direction in a plane parallel to that of the base plate. The free end portion of the bolt is provided with a longitudinal bore 14, said bored portion being split, as clearly shown at 15. Into the bore ofthe bolt extends the reduced portion -16 of a companion bolt 17. The diameter of the screw threaded body portion 18 of the companion bolt corresponds to that of the screw threaded portion of the bolt 13. Both bolts are made of electric conducting material preferably metal, the reduced portion 16 o the companion bolt being slidable in thev bore of the bolt 13 but maintaining always electric contact with the bolt 13. The latter bolt is split to permit of easy sliding of the said companion bolt. Over'the two bolts is drawn a sleeve 19 of electric insulating material, preferably hard frubber, one end of saidy sleeve abutting .against the lug 11..

This sleeve is provided with interior screw threads near both of its ends; those o n one end meshing with the threads of the bolt 13 and those on the other end with the threads member to the base plate, said screws being A insulated from the said frame member by insulating disks 26. .The frame member` 23 is provided with a downwardly extending lug 27 having a screw threaded hole' 28 in alinement ywith the hole 12 in the lug 11. With the threads of the hole 28 mesh those of a set screw 29, having a contact point 30 in proximity of and in registering position with the contact point 21 on the companion bolt 17.

One end of the heating coil 22v is electrically connected with the lug 11, and its other end with the frame member 23. From this it appears that the said coil is"connected in a shunt around the switch 'contact points.

As illustrated in the diagram in Fig. 6, one terminal o'f an electric battery 31 is connected by a battery conductor 32 withone terminal of an incandescent lamp 33, the

` other terminal of which is connected by an electric conductor 34 with the frame member 23. The base plate 10, on the other hand, is connected by an electric conductor 35 with the ,other terminal of the battery.

With the connections described, current will normally low from the battery 31 through the wire 32 to the lamp 33, thence through wire 34 to frame member 23, through the heating coil 22 to the base plate 10,. and through the wire 35 back to the battery. The heating coil is .thus in series with the lamp, and its relative resistance is so high that the amount of current passing through the circuit will be insufficient to light the lamp. rlihe current flowing through the circuit, however,

will be sufficient to heat the coil 22 and` thus the insulating sleeve 19, so that the latter will expand mainly in the direction of its longitudinal axis until the-contact point 21 on the companion bolt 17 is brought into engagement with the contact point 30 on the set screw .29. Upon such e11- gagement, a vlow resistance shunt is formed around theheating coil, and the current will How from the battery 31 by conductor 32 to the lamp' 33, thence by conductor 34 to frame member 23, through set screw? 29 to bolts 17 and 13, and through base plate 10 and conductor 35 back to the battery. rlhe low resistance circuit thus formed permits a light current to pass and the lamp will ash but brightly. Inasmu'ch as the resistance of the coil is very hi h compared to that of the circuit formed w en the contacts are in engagement, only-a small or practically no. current will flow throu h the heating coil so that the latter and the insulating sleeve will cool, with the result that the said sleeve contracts and breaks the contact between the points 21 and 30. ln this manner the heating coil is again interposed in the circuit, with the result that the lampis dimmed or becomes entirely dark. The cycle of operations now described is then repeated.L

rlhe device as herein described is particularly useful in connection with pocket flash lights of the cylindrical type, in which the battery is held in place by a spring bearing against the sameand against the screw cap at -the bottomA of the casing. rlhe device may be conveniently inserted into such flash lights, its frame member 23 and base plate 10 being interposed in the circuit without the aid of any additional wires, clamps, etc. l

inasmuch as only linear expansion of the insulating sleeve 19 is necessary to close the switch, the device can be conveniently opsol erated by low electric power circuits, in con- ,j

tradistinction to the devices heretofore in use in which the expansion device had to be bent or bowed to make contact, or inv other words necessitated considerable power and thus heat energy for operation.

lt is obvious -that `while herein both the base plate 10 and the frame member 23 have been described as being made of electric conducting material, these partsmay be made of other material, and the conductors 34 and 35 connected with theset screw 29 and bolt 13 without departing from the invention, which lies mainly in the provision of an expansionv device making and `breaking the Contact by motion in the direction of its longitudinal axis. f

rlhe sleeve 19 has been made of Ainsulating material ,for two reasons, to wit: first, it permits` uninsulated wire to be used m constructing the heating coil, second, its coeiiicient of expansion is considerably more favprable than lthose of the metallic expansion members heretofore generally employed.

What l claim is:

1. Inthermo-dynamic switch, the combination with a base, of a frame mounted thereon, a stationary-contact point on said Aframe, a bolt on said base extending toward said stationary contact point and provided with la bore, the bored portion of said bolt being split, a, second bolt having its inner end slidablyT arranged in the bore of said first bolt and carrying upon its outer end a contact point disposed inproXimity of said stationary contact point, a sleeve drawn over said-two bolts and/'fastened thereto, one end of said sleeve abuttin against said base, and aheating coil woun upon said sleeve-andr l 5 material, of a, frame of electric conducting material mounted thereon and insulated therefrom, a stationary contact point on saidA frame, a bolt on said base extending toward said stationa contactpoint and provided with a bore, t e bored portion of said bolt being s lit,- a second bolt having its inner end sli ably arranged in the bore of said rst bolt, and carrym upon its outer end a contact point dispose in proximity of said stationary contact point, both bolts being made of electric conducting material, a sleeve of electric insulating material drawn over said two bolts and fastened thereto, one end of said sleeve Iabuttin against said base, and a heatin coil woun upon said sleeve and connecte in shunt around said contact points to said base and frame.V

3. In a thermo-dynamic switch, the comloination with a. base, of a frame mounted thereon, a stationary Contact point on said frame, an expansion member upon said base having one of its ends abutting against said base and its other end free in proximity of said stationary contact point, a bolt extendp ing through said expansion member made of two continuously contacting sections, one of which is fixed to and in electric contact with said 'base and 'the other one fixed to the free end of said expansion member, thereby forming a mova le contact point, and a heating coil wound. upon said .expansion member and connected to saidbase and said stationary contact point.

4. A thermo-dynamic switch, including a stationary contact point, an expansion member having a fixed end and a free end in proximity of said contact point, la bolt extending through said expansion member made of two continuously contacting sections, one of which is fixed to the fixed end of said expansion member and the other one secured to the free end of said expansion member, thereby forming a movable contact point, and a heating coil wound upon said expansion member and connected to the xed section of said bolt and said stationary contact point.

Sign New York and State of New York, this 26th day of Feb., A. D. 1918. y'

HARTWELL W. WEBB.

ed a't New York, in the county of 

